Gate Oxide Thickness Control in Shallow Trench Isolation
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Solution Overview
Problem
High aspect ratio shallow trench isolation (STI) in semiconductor manufacturing leads to oxide thinning and increased silicon defects due to high stress from high density plasma (HDP) deposition, affecting gate oxide integrity and device reliability.
Innovation Solution
A dry oxidation process using a gas flow with oxygen and a low molecular weight chloro-carbon, such as 1,2-dichloroethene, is employed to form a gate oxide layer with a thickness ratio of 0.6:1 to 0.8:1 over active regions and corners, reducing physical stresses and enhancing oxide growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high density plasma (HDP) deposition is used to fill shallow isolation trenches with high aspect ratios, then fill quality improves, but oxide thinning occurs on the corners of active regions and stress increases causing silicon defects
Solution Approach 1:
The patent changes the chemical composition parameters of the oxidation gas by introducing low molecular weight chloro-carbons (such as 1,2-dichloroethene) at controlled concentrations (2%-6% of total gas flow). This parameter modification alters the oxidation kinetics to produce thicker, more stress-resistant gate oxide at critical corner regions while maintaining compatibility with HDP-filled isolation trenches.
Solution Approach 2:
The low molecular weight chloro-carbon acts as an intermediary substance in the oxidation process. It mediates between the oxygen and the silicon surface, modifying the oxidation mechanism to reduce stress accumulation and prevent oxide thinning at corners. The chloro-carbon decomposes during oxidation, releasing chlorine that affects the oxide growth characteristics without compromising the overall process.
2Reliability
If HDP oxide is used in isolation regions, then isolation effectiveness improves, but stress on trench walls increases causing silicon defects and higher defect densities
Solution Approach 1:
The patent modifies the oxidation process parameters by introducing chloro-carbon additives that change the stress characteristics of the grown gate oxide. This parameter change allows the gate oxide to better accommodate the stress from HDP isolation regions, reducing the transmission of stress to the silicon substrate and minimizing defect formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution increases gate oxide thickness and integrity, improving breakdown voltage, reducing defect densities, and increasing device yields while integrating well with standard manufacturing processes.
Implementation Method 1
A dry oxidation process is used to form a gate oxide layer over the active region and the corner
Implementation Method 2
The dry oxidation process employs a gas flow including oxygen and a low molecular weight chloro-carbon
Data Source
AI summary
One aspect of a semiconductor device includes an active region located in a semiconductor substrate and having an isolation region located therebetween. The active regions have corners adjacent the isolation region. An oxide layer is located over the active regions and the corners, which may also include edges of the active regions, and a ratio of a thickness of the oxide layer over the corners to a thickness of the oxide layer over the active regions ranges from about 0.6:1 to about 0.8:1. A gate is located over the active region and the oxide layer.